This is from an 8495E, but it should be the same:
First, press the CONFIG button.
Then, press side button #6 twice to get to the SYNC menu.
Then:
Press side button #2 to toggle between NRM and NTSC
-or-
Press side button #3 for DEFAULT SYNC
-or-
Press side button #4 to toggle between NRM and PAL
You could also try plugging a monitor into the back to see what you're doing.